Human Evolution Flashcards
Humans – position in phylogeny
What are;
Gnathostomes
Tetrapods
Amniotes
Mammals
Gnathostomes: Vertebrates with jaws
Tetrapods: Gnathostomes with limbs and feet
Amniotes: Tetrapods with eggs adapted for land
Mammals: Amniotes with hair and that lactate
Order Primates
What are eutherians?
Primates?
What are Anthropoids?
What are Hominoids?
Eutherians: Placental mammals
PRIMATES: Eutherians with hands and feet adapted for grasping
No claws
Large brain
Short jaws
Stereo vision
Anthropoids: Primates with a somewhat opposable thumb
Hominoids: Anthropoids with a fully opposable thumb – apes and humans
Hominoidea – ‘higher primates’
Hominins and panins evolved from a common ancestor
Some differences between modern Hominins and Panins
Human
Steep forehead, flat face
Large brain (14-1600cc), large cranial size at birth
Small canines, large molars
Fully bipedal – foramen magnum under skull
Chimpanzee
Low forehead, projecting face
Small brain (400cc)
Large canines, small molars
Partially bipedal – foramen magnum at back of skull
The earliest hominins (pinch of salt)
Three ‘Candidate’ groups of fossils
Very limited material
Fossils from 6 – 4.5 mya
Apparent lack of early Panin fossils
Sahelanthropus tchadensis
Orrorin tugensis
Ardipithecus ramidus
Archaic hominins from east Africa: Australopithecus
Several species
A. afarensis discovered in 1974
‘Lucy’
Ethiopia
4.5-4.0 mya
1m tall
Fully bipedal
But small brained relative to modern humans 400-500cc
Bipedal locomotion
Key adaptation in hominids
Anthropoid ancestors were arboreal (30-35 mya)
Didn’t evolve in one go
Long distance bi-pedalism only evolved 1.9 mya
A pre-adaptation for other hominid features
What is the Savannah theory?
What is the Aquatic theory?
*climate becoming warmer and therefore larger open areas, moving with two legs gives less surface area for the sun to heat, important for thermoregulation. In a big open area its better to see further away to see predators= larger field of view.
*Walking on two legs to allow our ancestors to wade into swampier areas and the sea to find food.
Describe the functional morphology of Australopithecus afarensis
Brain bigger than chimpanzee but so is body
Small incisors and big molars suggests a diet of tough food
Capable of bi-pedal walking but only over short distances
Large zygomatic arches – massive jaw muscles
Rectangular (or U-shaped) arrangement of teeth
Prognathus (protruding) jaw
Australopithecus garhi
East Africa 2.5 mya
Even larger chewing teeth
‘Megadont’
Fossil animal bones with scrape-marks found in same site
First evidence of tool use and de-fleshing animal carcases
Tool use
Not unique: May have evolved before large brain size
Change to bipedalism allowed selection on hands
High dexterity a pre-adaptation for large brains?
Cognitive skills an exaptation?
Manual dexterity in humans:
Power grip
Precision grip
‘Robust’ and ‘gracile’ australopiths
Australopithecus africanus, a gracile australopith 3.0 – 2.5 mya in Southern Africa .
Light skeleton
Bipedal but possibly also arboreal
Paranthropus spp.,a robust australopith 2.3 – 1.2 mya, Southern Africa.
(Paranthropus - ‘beside man’)
Transitional hominins:
Earliest examples of genus Homo
600-700cc brain
‘Homo’ habilis
‘Handyman’
2.4 mya Olduvai gorge, Tanzania
Controversial; may be an australopith
Possibility of spoken language based on false assumption about brain morphology (Broca’s area)
500-800cc brain
H. rudolphensis
Bigger wider, flatter face
1.9 mya Lake Turkana, Kenya
Large chewing muscles
But very little known about this species
Pre-modern Homo
Homo ergaster, 1.5 mya, Kenya
Slender, gracile
Fully bipedal
Large brain
Low sexual dimorphism
Homo erectus, Kenya
Extinct 200,000 years ago (0.2 mya)
May be the direct ancestor of modern humans
First to migrate out of Africa, 1.5 mya
One of the descendent species of Homo erectus as well as modern humans was Homo neanderthalensis
Many similarities with modern humans
Evidence for interbreeding with early H. sapiens in Europe
But modern humans not directly descended from Neanderthals.
Evidence of making tools
Modern humans may have outcompeted the Neanderthals.
